docs: def handle_unset_command(self, line: str, position: int, tokens: ParseResults) -> ParseResults:
          """Handle an ``UNSET X`` statement or raises an exception if it is not already set.
  
          :raises: MissingAnnotationKeyWarning
          """
          key = tokens['key']
          self.validate_unset_command(line, position, key)
          del self.annotations[key]
          return tokens